It has been conventionally known digital mixers performing processing such as adding an effect or mixing by digital signal processing with respect to audio signals of plural series inputted through plural input ports and outputting the processed signals (for example, see PTL1, PTL2, and the like). These digital mixers have plural input ports performing processing such as inputting an analog audio signal and converting it into a digital audio signal, and plural input channels performing processing such as adding an effect or level control on the digital audio signal, and also have an input patch connecting a desired input port to each of the input channels. The user plugs, for example, a vocal microphone into an input terminal corresponding to a first input port, and performs setting so that the first input port and the first channel are connected by the input patch. Thus, the following processing can be carried out, that is, performing various types of signal processing on a vocal audio signal inputted by the microphone in the first channel, appropriately mixing the processed signal, and outputting the mixed signal.
To each input port described above, parameters for controlling operation of this input port are set by the user. The parameters set to the input port are retained corresponding to this input port, and thereafter, this input port operates according to these parameters. These parameters can be rewritten according to an instruction from a central processing unit (CPU) of the digital mixer.